Vehicle seat

ABSTRACT

The present vehicle seat has a framework  14 , a plurality of zigzag springs  25, 25  attached between side frame member  17, 17  of the framework  14 , and a height control mechanism  38  moving the framework  14  up and down relative to a vehicle body. The spring tip end  26  of each of the springs  25  is arranged at a position adjacent to the center line which vertically divides the side member  17 , so that the distance between the spring tip end  26  and the center line is shorter than the distance between the spring tip end  26  and the upper edge  30  of the side member  17 . Arms  51, 52  and an elongated link  53  of the height control mechanism  38  are arranged outside the side member  17.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a vehicle seat, and more particularly,relates to the frame structure of a seat bottom of a vehicle seat.

BACKGROUND ART OF THE INVENTION

As a prior art, Japanese Utility Model Application Laid-Open No. 5-35458discloses a seat bottom of a vehicle seat, which comprises: a frameworkincluding a pair of left and right side frame members extending in theback-and-forth direction, a front frame member fixed between frontportions of the side frame members, and a rear frame member fixedbetween rear portions of the side frame members; a plurality of zigzagsprings positioned between the front frame member and the rear framemember, and having spring tip ends attached at the middle portionbetween the front portion and the rear portion of the side frame member;a cushion attached on the framework with the springs; and a heightcontrol mechanism moving the framework up and down relative to a vehiclebody.

The prior art has such a disadvantage that the thickness in the verticaldirection of the seat bottom is thick. It will be described below. Asshown in FIGS. 23 and 24, the framework 100 of the prior art has abracket 102 fixed to a bottom 101 of the framework 100, and the bracket102 is connected to a slide rail 104 by way of a height controlmechanism 103. The height control mechanism 103 has a leg portion 105fixed to the bracket 102, an arm 107 connected to the tip of the legportion 105 by a shaft 106, an interlocking shaft 108 to which the baseportion of the arm 107 is fixed, an operating dial 109, an output gear110 arranged to be rotated by the operating dial 109, and a sector gear111 meshed with the output gear 110 and fixed to the interlocking shaft108. The dial 109 is supported by a bracket 112 of the slide rail 104.

In the case of the prior art with the above structure, the framework 100has the integrally fixed bracket 102, and therefore, the vertical heightof the framework 100 is shown by H. Therefore, the zigzag spring 113 ispositioned at a higher position of the framework 100, and the positionof the cushion that is mounted on the spring 113 also inevitably becomeshigh, so that the thickness in the vertical direction of the seat bottomis increased.

Furthermore, in the case of the prior art, the fact that almost allmembers of the height control mechanism 103 are provided at positionslower than the upper end of the bracket 112 of the slide rail 104 isalso the reason why the vertical thickness of the seat bottom isincreased.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved vehicleseat that overcomes the disadvantage of the prior art.

In order to achieve this object, a vehicle seat is provided, whichcomprises: a framework composed of a pair of left and right side framemembers that extend in the back-and-forth direction, a front framemember that has left and right side plates fixed to the front portionsof the side frame members, and a rear frame member that has left andright side plates fixed to the rear portions of the side frame members;a plurality of zigzag springs that are positioned between the frontframe member and the rear frame member, and have spring tip endsattached at the middle portion between the front portion and the rearportion of the side frame member; and a height control mechanism thatmoves the framework up and down relative to the vehicle body, and whichis characterized in that each of the spring tip ends is arranged at aposition near the center line vertically dividing the side frame member,and the distance between the spring tip end and the center line is madeshorter than the distance between the spring tip end and the upper edgeof the side frame member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vehicle seat according to the presentinvention;

FIG. 2 is a right side view of a framework of a seat bottom of thevehicle seat attached to a vehicle body;

FIG. 3 is an exploded illustration of the framework and other members;

FIG. 4 is a left side view of a left side frame member of the framework;

FIG. 5 is a left side view showing the framework and a cushion mountedon the framework;

FIG. 6 is a right side view showing the framework and the cushionmounted on the framework.

FIG. 7 is a vertical cross sectional front view of the seat bottom;

FIG. 8 is an exploded illustration of spacers to be attached to the seatbottom and front and rear connecting members;

FIG. 9 is an enlarged illustration of the connecting members;

FIG. 10 is a partial enlarged view of the rear connecting member;

FIG. 11 is an enlarged illustration of the left side rear portion of theframework;

FIG. 12 is a vertical cross sectional front view showing a sector gearof a height control mechanism of the seat bottom and an interlockinglever;

FIG. 13 is a vertical cross sectional front view of a reduction gearmechanism and an operating dial of the height control mechanism;

FIG. 14 is a vertical cross sectional front view of the left side frameand a frame cover;

FIG. 15 is an enlarged illustration of a front frame member of theframework and a zigzag spring;

FIG. 16 is a vertical cross sectional front view showing a reinforcingupward rib and a reinforcing downward rib of the front frame member;

FIG. 17 is the X—X cross sectional view in FIG. 5;

FIG. 18 is a cross sectional view of a shaft sleeve by which an arm ofthe height control mechanism is attached to the side frame member;

FIG. 19 is a plan view showing the state of attaching of a torsion barspring of the height control member;

FIG. 20 is a right side view showing the state of attaching of thetorsion bar spring;

FIG. 21 is a partially cut-off illustration showing the state ofattaching of the torsion bar spring;

FIG. 22 is a graph view showing the relation between the angle of twistof the torsion bar spring and the torque; and

FIG. 23 and FIG. 24 are drawings of a publicly known example showing thevehicle seat disclosed in Japanese Utility Model Application Laid-OpenNo. 5-35458.

BEST MODE FOR CARRYING OUT THE INVENTION

One mode of the present invention will be described by referring todrawings. The vehicle seat 10 according to the present inventionincludes a seat bottom 12 which is slidably attached to a vehicle body11 and a seat back 13 which is rotatably supported by the seat bottom12. The seat bottom 12 has a framework 14 which is rectangular in theplan view, and as shown in FIG. 3, the framework 14 is substantiallycomposed of a front frame member 15, a rear frame member 16, and uprightside frame members 17, 17 extending in the back-and-forth direction ofthe seat 10.

The front frame member 15 is a laterally elongated rectangularpan-shaped frame, and as shown well in FIG. 15, has a corrugated bottomplate 20 with a laterally extending reinforcing upward rib 18 and alaterally extending reinforcing downward rib 19, and upright side plates21, 21. As shown in FIG. 16, the downward rib 19 is provided at themiddle portion except for the left side portion and the right sideportion of the bottom plate 20, and is positioned at the rear side ofthe upward rib 18. The side plates 21, 21 are fixed to the frontportions of the side members 17, 17 by bolt-nut means, welding means orthe like, respectively.

Side plates 22, 22 of the rear member 16 are fixed to rear portions ofthe side members 17, 17 with bolts 23, 24, respectively. Between middleportions, a plurality of laterally extending zigzag springs 25, 25 areprovided. Tip ends 26, 26 of the springs 25, 25 are engaged with aplurality of mounting holes 27, 27 formed in the middle portions of theside members 17, 17, respectively.

The springs 25, 25 are arranged between the front member 15 and the rearmember 16 as shown in FIGS. 5 to 7. Each of the mounting holes 27 isarranged at a position adjacent to the center line vertically dividingthe side frame member 17, or a position under the center line. It isdesired that the springs 25, 25 and the bottom plate 20 of the frontmember 15 have approximately the same height. On the framework 14 withthe springs 25, 25, a cushion 28 made of urethane or the like isattached. In the present invention, in the interior 29 of the middleportion of each of the side members 17, as is clear from FIG. 7, nomovable member of a height control mechanism is provided, which maycause damage to the cushion 28. Therefore, it becomes possible that eachof the springs 25 is separated from the upper edge 30 of the side member17 to lower the position of the cushion 28. This construction bringssuch an advantage that the height of the seat bottom 12 can be loweredwithout thinning the cushion 28 on the springs 25, 25, which supportsthe hip of a driver or a passenger. Accordingly, the hip of the driveris comfortably supported by the excellent cushioning performance of thesprings 25, 25 and the cushion 28.

An outwardly extending flange 31 is integrally provided on at leastupper and front edges of each of the side members 17 with which thecushion 2B comes into contact. A base portion of the flange 31 is formedto have a gently curved corner 32 for preventing damages from beinggiven to the cushion 28. The rear portion of each of the side members 17is fixedly provided with a supporting portion 33 to which the seat back13 is attached.

As clear from FIG. 5, the length in the back-and-forth direction of thebottom plate 20 of the front frame member 15 is longer than the verticallength of the upright side plate 21 of the front member 15, andfurthermore, it is equal to or longer than the thickness of the cushion28. The front member 15 is positioned under the femoral region of thedriver or the passenger. The front member 15 has no substantialelasticity, and the femoral region is elastically supported only by thecushioning of the cushion 28. The front portion of the seat bottom 12does not require a great amount of elasticity, and therefore, thecomfortability of the front portion of the seat bottom 12 cansufficiently be ensured only by the cushion of the cushion 28. Thepan-shaped corrugated front member 15 has no elasticity, but instead ofthat, it has a high rigidity. The high rigidity of the front member 15resists the so-called “submarine phenomenon” where the driver sinks downin the front downward direction at the time of a vehicle accident or thelike, and keeps the driver at the normal position. Furthermore, the highrigidity of the front member 15 makes it unnecessary to provide areinforcing member that connects the middle portions of the side members17, 17 to each other.

As mentioned above, the framework 14 with the springs 25, 25 has a basicability for providing a high rigidity and a sufficient comfortability tothe seat bottom 12. Furthermore, the framework 14 with the springs 25,25 has no heavy structural member at the portion surrounded by fourmembers 15, 16, 17 and 17, and therefore, it can be manufactured to belight weight. Furthermore, each of the springs 25 is separated from theupper edge 30 of the side member 17, and therefore, the seat bottom 12can be made thin without damaging the comfortability.

In the present invention, the tip end 26 of each of the springs 25 isarranged at a position adjacent to the center line of the side framemember 17. This means that the change of the shape or profile of theupper edge 30 of the side member 17 has no effect on the elasticityproduced by the springs 25, 25, and means that the shape of the upperedge 30 can be designed while neglecting the cushioning performance ofthe seat bottom 12. Accordingly, in the present invention, the shape ofthe upper edge 30 can be designed while aiming at the holdingperformance and the performance of getting on and off that are requiredto the seat bottom 12. Generally, a high upper edge 30 brings a highholding performance and a low performance of getting on and off. In thecase of the design where the cushioning performance can substantially beneglected, both the holding performance and the performance of gettingon and off that are antinomic to each other can be achieved at a highgrade.

In FIG. 2, the vehicle seat 10 has a pair of lower rails 34 fixed to thevehicle body 11 and upper rails 35 slidably attached to the respectivelower rails 34. Spacer 37 is fixed to an upright bracket 36 of each ofthe upper rails 35, and the framework 14 is attached to the spacers 37,37 through the height control mechanism 38. The spacers 37 are used whennecessary. In the case of a vehicle such as a sports car, the spacers 37become unnecessary, and as shown in FIG. 6, the framework 14 is directlyattached to the brackets 36 through the height control mechanism 38.

As shown in FIG. 8, the spacers 37, 37 are fixed to each other by acentral connecting member 39 and a rear connecting member 40. Thecentral connecting member 39 is composed of two metal rods 41, 42 thatare fixed to each other at the central portions by welding. Tip ends 43,43 of the rod 41 and tip ends 44, 44 of the rod 42 are separated fromeach other in the back-and-forth direction. The central member 39 hassuch an advantage that a comparatively light weight and a comparativelyhigh rigidity are both provided. The tip ends 43, 44 preferably have aninside screw thread, and are fixed to the spacers 37, 37 with bolts 45,45 (FIG. 2), respectively.

The rear connecting member 40 is composed of a laterally extendingupwardly arched bridge 46 and bent portions 47, 47 which are angled toextend backward from both sides of the bridge 46. As shown in FIG. 10,the respective bent portions 47 have weld nuts 49, 49 fitted to holes48, 48 formed in the bent portions 47, and are fixed to the spacers 37,37 with bolts 50, 50. The bolts 50, 50 and the nuts 49, 49 are arrangedalong a straight line of about 45 degrees. The bolts 50, 50 which havethe relation of inclination are provided with the function of a diagonalbeam, and strongly resists against a force in any direction. Therefore,the bent portion 47 can be firmly fixed to the spacer 37 only by twobolts 50, 50.

The middle portions of the spacers 37, 37 are fixed to each other firmlyby the high rigidity of the central connecting member 39, and the rearportions of the spacers 37, 37 are firmly fixed to each other by therear connecting member 40. Therefore, as long as there arises no unusualsituation, it is unnecessary to provide a member for connecting thefront portions of the spacers 37, 37. The bridge 46 which bulges upwardmakes it easy to use the wide space under the seat bottom 12 which ismade by the spacers 37, 37. For example, the passenger who sits on therear seat can easily put the feet into the space from the lower side ofthe bridge 46.

As shown in FIGS. 2, 3 and 5, the height control mechanism 38 has a pairof front arms 51A, 51B, a pair of rear arms 52A, 52B, and a pair ofelongated links 53A, 53B that are extending in the back-and-forthdirection. Each lower end of the front arms 51A, 51B is rotatablyattached to the spacer 37 with a lower bolt 54, and each upper end ofthe front arms 51A, 51B is rotatably attached to an outside surface 56of the side frame member 17 with an upper bolt 55. Each lower end of therear arms 52A, 52B is rotatably attached to the spacer 37 with a lowerbolt 57, and each central portion of the rear arms 52A, 52B is rotatablyattached to the outside surface 56 of the side member 17 with a fastener58, and upper ends of the rear arms 52A, 52B are rotatably connected torear ends of the elongated links 53A, 53B with upper bolts 59,respectively. When the links 53A, 53B moves in the back-and-forthdirection, the arms 51A, 51B, 52A and 52B rotate about the lower bolts54, 57, and the seat bottom 12 substantially moves in the verticaldirection. Four arms and two links are positioned outside the side framemembers 17, 17, respectively, and therefore, they do not interfere withthe cushion 28.

As shown in FIGS. 5, 6 and 11, the elongated links 53A, 53B areextending in the back-and-forth direction outside the side frame members17, 17, respectively. The front end of the left link 53A is connected toa sector gear 60A with a connecting pin 61A as shown in FIGS. 12, 20.The sector gear 60A is positioned between the left side member 17 andthe left side plate 21 of the front frame member 15 as shown in FIG. 16.The sector gear 60A is fixed, as shown in FIG. 12, to the left portionof a lateral interlocking shaft 62 which is rotatably provided betweenthe side members 17, 17. The connecting pin 61A passes through a leftcircular arc slot 63A formed in the left side member 17, for connectingthe left link 53A positioned outside the left side member 17 and thesector gear 60A positioned inside the left side member 17. The rotationof the sector gear 60A brings the rotation of the interlocking shaft 62and the movement in the back-and-forth direction of the left link 53A.The sector gear 60A is positioned between the left side member 17 andthe front member 15, and therefore, it can be arranged at a position ofthe same height as the side member 17 without interfering with thecushion 28.

As shown in FIGS. 6 and 12, the front end of the right link 53B isconnected to an interlocking lever 60B with a connecting pin 61B. Theinterlocking lever 60B is positioned between the right side member 17and the right side plate 21 of the front frame member 15, and is fixedto the right portion of the interlocking shaft 62. The connecting pin61B passes through a right circular arc slot 63B formed in the rightside member 17, for connecting the right link 53B positioned outside theright side member 17 and the interlocking lever 60B positioned insidethe right side member 17. When the interlocking shaft 62 is rotated bythe rotation of the sector gear 60A, the right link 53B is moved in theback-and-forth direction through the interlocking lever 60B. Theinterlocking lever 60B is positioned between the right side member 17and the front frame member 15, and therefore, it can be arranged at aposition of the same height as the side member 17 without interferingwith the cushion 28.

The sector gear 60A and the interlocking lever 60B are arranged insidethe side members 17, 17, respectively, and therefore, it is possible tofix the sector gear 60A and the interlocking lever 60B to theinterlocking shaft 62 by welding means or the like before attaching theinterlocking shaft 62 to the side members 17, 17. As shown in FIGS. 15and 16, the interlocking shaft 62 is laterally extending by using thelower space formed by the reinforcing upward rib 18 of the front framemember 15. This increases the degree of freedom of the attachingposition of the interlocking shaft 62 and the front frame member 15.Furthermore, the reinforcing downward rib 19 of the front member 15 alsohas the function for preventing the cushion 28 mounted on the framework14 from overrunning toward the interlocking shaft 62.

As shown in FIGS. 5 and 13, a reduction gear mechanism or brakemechanism 64 is provided outside the front portion of the left sidemember 17. The reduction gear mechanism 64 has an output shaft 65projecting to the inside or to the right and an input shaft 66projecting to the outside or to the left. An operating dial 67 of theheight control mechanism 38 is fixed to the outer end of the input shaft66, and an output gear 68 is fixed to the output shaft 65. The outputgear 68 is contained in a concave portion 69 formed in the left sidemember 17 to be positioned outside the left side member 17. The sectorgear 60A is meshed with the output gear 68 through a window 70 formed inthe rear peripheral wall of the concave portion 69. The rotation of thedial 67 is transmitted to the sector gear 60A through the reduction gearmechanism 64, and consequently, the elongated links 53A, 53B move in theback-and-forth direction at the same time to control the height of theseat bottom 12. Furthermore, because of the braking function of thereduction gear mechanism 64, it does not occur for the output gear 68 torotate by the external force received from the sector gear 60A.Furthermore, it is also possible to rotate the output gear 68 by usingan electric motor instead of the operating dial 67.

The output gear 68 of the reduction gear mechanism 64 is positionedoutside the side member 17. Therefore, it is possible to attach theoutput gear 68 to the output shaft 65 of the reduction gear mechanism 64in advance. Furthermore, the front side of the output gear 68 issurrounded by the front peripheral wall of the concave portion 69, andtherefore, it is possible to prevent goods or the like contained underthe seat bottom 12 from coming into contact with the output gear 68.

As shown in FIGS. 17, 18, the fastener 58 for attaching the rear arm 52A(52B) to the side frame member 17 comprises a stepped shaft sleeve. Thesleeve 58 has a first head portion 71 formed at the tip end in advance,a large diameter body 72 which rotatably supports the side member 17, asmall diameter body 73 which rotatably supports the rear arm 52A, and acentral through hole 74. After attaching the side member 17, the reararm 52A, and a washer 75 to the fastener 58, a second head portion 76 isformed by caulking work at the tip of the fastener 58. After attachingthe rear arm 52A to the side member 17 with the fastener 58 rotatably,the bolt 24 is inserted into the through hole 74 to be screwed into anut 77 welded to the side plate 22 of the rear frame member 16, therebythe rear frame member 16 is fixed to the side member 17.

As mentioned above, when three comparatively large and heavy members areconnected or fixed by using the shaft sleeve 58 and the bolt 24, severalexcellent advantages can be obtained. A first advantage is that theassembly of each member becomes easy. When assembling three largemembers only by one bolt, it becomes a very difficult work to alignthree holes which a re formed in the respect iv e members. A secondadvantage is that it is possible to prevent the lowering of strength ofeach member. If a first member and a second member are fixed by a firstbolt, and after that, the first member and a third member are fixed by asecond bolt, it is necessary to form two holes through which two boltspass, in the first member. The two holes lower the strength of the firstmember.

As shown in FIGS. 19 to 21, the seat bottom 12 has elastic means 78which assists the operation for moving the seat bottom 12 upward by theheight control mechanism 38. The elastic means 78 comprises two torsionbar springs 79, 79. First tip ends 79A, 79A of the springs 79, 79 areengaged with a hook member 80A fixed to the left side frame member 17,and second tip ends 79B, 79B of the springs 79, 79 are engaged with ahook member 80B fixed to the interlocking shaft 62, and consequently,the interlocking shaft 62 is urged in the counterclockwise direction inFIG. 20. The heavy seat bottom 12 to which the body weight of the driveris applied is easily moved upward with the assistance of the elasticityof the springs 79, 79.

The hook member 80B is fixed to the right portion of the interlockingshaft 62, and the distance between the hook member 80A and the hookmember 80B is lengthened. The long torsion bar springs 79, 79 providedbetween the hook member 80A and the hook member 80B can produce a strongelasticity that counteracts the body weight of the driver. Furthermore,the fluctuation of torque of the long torsion bar springs 79, 79 becomessmall. In the case of a small fluctuation of torque, a uniformrotational torque can be given to the interlocking shaft 62 regardlessof the position of height of the seat bottom 12, and therefore, thefluctuation of the operating load of the operating dial 67 is made smalldecreased.

Additionally, the fluctuation of torque of the elastic means 78 isfurther decreased by using plural springs. In FIG. 22, the line L1 showsthe torque that is obtained from a single torsion bar spring S1 with adiameter of 5 mm. In the case of the present embodiment, theinterlocking shaft 62 rotates by about 25 degrees when the seat bottom12 moves from the lowest position to the highest position. Furthermore,it is desired to give a torque of about 210 Kgf/cm to the interlockingshaft 62. The spring S1 produces a torque of about 210 Kgf/cm whentwisted by about 43 degrees. However, when the spring S1 is twisted inthe range R1 of about 25 degrees on the basis of about 43 degrees, thespring S1 produces a torque of a maximum of about 275 Kgf/cm to aminimum of about 150 Kgf/cm.

On the other hand, as an example, the elastic means 78 of the presentinvention is composed of a spring S2 of a diameter of 4 mm having thetorque line L2 and a spring S3 of a diameter of 3.5 mm having the torqueline L3. The spring S2 is used in the range R2 of the torsion angle ofabout 50 degrees to about 75 degrees, and the spring S3 is used in therange R3 of the torsion angle of about 23 degrees to about 48 degrees.The dotted line L4 shows a composite torque composed of a torque of thespring S2 in the range R2 and a torque of the spring S3 in the range R3.As clear from the comparison between the dotted line L4 and the line L1,the fluctuation of torque of the elastic means 78 that has two springsis very small.

As shown in FIGS. 2, 7, frame covers 81, 81 are respectively attached tothe outer portion of the side frame members 17, 17 to cover the movablemembers arranged outside the side frame members 17, 17. Each cover 81has an upright plate 82 and a bent portion 83 extending to the insidefrom three side edges except for the rear side edge of the upright plate82. The bent portion 83 is positioned at the interior side of the flange31 of the side member 17 so that the tip of the bent portion 83 does notcome into contact with the cushion 28. A gently curved corner 84 betweenthe upright plate 82 and the bent portion 83 is positioned at theoutside of the tip of the flange 31 to decrease the opportunity for thecushion 28 to come into contact with the tip of the flange 31.

Several portions of the periphery of the cover 81 are dented by pressworking to form contact faces 85, 85 (FIGS. 11, 12). The inner curvededge 86 of the contact face 85 is connected to the upright plate 82 ofthe cover through a slant face 87, and the outer edge 88 of the contactface 85 becomes the end face. Therefore, it is possible to form thecontact face 85 not by press working of deep-drawing whose cost is highbut by normal press working. The contact face 85 is fixed to the sideframe member 17 by fastening means such as a screw, a bolt, a rivet, orwelding.

At the outer surface of the cover 81, an approximately U-shaped engagingrod 89 is welded. As shown in FIG. 7, a hook member 91 which is sewnonto the tip end of an outer skin 91 of the cushion 28 is engaged withthe engaging rod 89. At the outer surface of the cover 81, no member issubstantially provided except for the rod 89. This brings severaladvantages. First, the degree of freedom of the attaching position ofthe rod 89 increases. Second, the welding portion can be made large, andtherefore, the attaching strength of the rod 89 can be enhanced. Third,the length in the back-and-forth direction of the rod 89 can be madelong, and therefore, the man-hour of the attaching work of the outerskin 90 can be reduced. Fourth, the length in the back-and-forthdirection of the rod 89 can be made long, and therefore, the appearanceof the outer skin 90 is improved.

What is claimed is:
 1. A vehicle seat comprising: a framework whichincludes a pair of left and right side frame members extending in aback-and-forth direction, a front frame member having left and rightside plates fixed to front portions of the side frame members,respectively, and a rear frame member having left and right side platesfixed to rear portions of the side frame members, respectively; aplurality of zigzag springs positioned between the front frame memberand the rear frame member, each of said zigzag springs having spring tipends attached at middle portions between the front portions and the rearportions of the side frame members; and a height control mechanismarranged to move the framework up and down relative to a vehicle body;wherein each of said spring tip ends is provided at a position adjacentto a center line which vertically divides the side frame member, so thata distance between the spring tip end and the center line is shorterthan a distance between the spring tip end and an upper edge of the sideframe member.
 2. The vehicle seat according to claim 1, wherein saidheight control mechanism has no movable member positioned between themiddle portions of the side frame members.
 3. The vehicle seat accordingto claim 1, wherein said height control mechanism comprises front andrear arms which connect the framework to the vehicle body, an elongatedlink which is connected to the rear arm and extends in theback-and-forth direction, and operating means that is connected to afront end of the elongated link to move the elongated link in theback-and-forth direction, and wherein said front arm, the rear arm, andthe elongated link are arranged outside the side frame member.
 4. Thevehicle seat according to claim 3, wherein said operating meanscomprises an output gear which is rotated by hand and a link gear whichis meshed with the output gear and is connected to the front end of theelongated link, and wherein said link gear is positioned between thefront portion of the side frame member and the side plate of the frontframe member.
 5. The vehicle seat according to claim 4, wherein saidoutput gear is positioned outside the side frame member, and whereinsaid side frame member has a window which makes it possible to mesh theoutput gear with the link gear.
 6. The vehicle seat according to claim4, wherein said height control mechanism further comprises elastic meanswhich urges the link gear in a given direction, and said elastic meansincludes a laterally extending torsion bar spring which has a lengthlonger than half the distance between the side frame members.
 7. Thevehicle seat according to claim 6, wherein said elastic means comprisestwo torsion bar springs.
 8. The vehicle seat according to claim 7,wherein said two torsion bar springs are used in the state of producingtorque different from each other.
 9. The vehicle seat according to claim3, further comprising a frame cover attached to an outer portion of theside frame members to cover the elongated link to prevent a cushion fromcoming into contact with the elongated link.
 10. The vehicle seataccording to claim 3, wherein said side frame member and said rear armare connected to each other by caulking one end of a shaft sleeve, andthe rear frame member and the side frame member are connected to eachother by a bolt which is inserted into a central through hole of theshaft sleeve.
 11. The vehicle seat according to claim 3, wherein saidoperating means comprises an output gear which is rotated by motor powerand a link gear which is meshed with the output gear and is connected tothe front end of the elongated link, and wherein said link gear ispositioned between the front portion of the side frame member and theside plate of the front frame member.
 12. The vehicle seat according toclaim 11, wherein said output gear is positioned outside the side framemember, and wherein said side frame member has a window which makes itpossible to mesh the output gear with the link gear.
 13. The vehicleseat according to claim 11, wherein said height control mechanismfurther comprises elastic means which urges the link gear in a givendirection, and said elastic means includes a laterally extending torsionbar spring which has a length longer than half the distance between theside frame members.
 14. The vehicle seat according to claim 13, whereinsaid elastic means comprises two torsion bar springs.
 15. The vehicleseat according to claim 14, wherein said two torsion bar springs areused in the state of producing torque different from each other.
 16. Avehicle seat comprising: a framework which includes a pair of left andright side frame members extending in a back-and-forth direction, afront frame member having left and right side plates fixed to frontportions of the side frame members, respectively, and a rear framemember having left and right side plates fixed to rear portions of theside frame members, respectively; and a height control mechanismarranged to move the framework up and down relative to a vehicle body,said height control mechanism comprising front and rear arms whichconnect the framework to the vehicle body, an elongated link which isconnected to the rear arm and extends in the back-and-forth direction,and operating means that is connected to a front end of the elongatedlink to move the elongated link in the back-and-forth direction; whereinsaid side frame member and said rear arm are connected to each other bycaulking one end of a shaft sleeve, and the rear frame member and theside frame member are connected to each other by a bolt which isinserted into a central through hole of the shaft sleeve.
 17. A vehicleseat comprising: a framework which includes a pair of left and rightside frame members extending in a back-and-forth direction, a frontframe member having left and right side plates fixed to front portionsof the side frame members, respectively, and a rear frame member havingleft and right side plates fixed to rear portions of the side framemembers, respectively; a height control mechanism arranged to move theframework up and down relative to a vehicle body, said height controlmechanism comprising front and rear arms which connect the framework tothe vehicle body, an elongated link which is connected to the rear armand extends in the back-and-forth direction, and operating means that isconnected to a front end of the elongated link to move the elongatedlink in the back-and-forth direction; said operating means comprising anoutput gear which is rotated by hand and a link gear which is meshedwith the output gear and is connected to the front end of the elongatedlink; said height control mechanism further comprising elastic meanswhich urges the link gear in a given direction, and said elastic meansincluding a laterally extending torsion bar spring which has a lengthlonger than half the distance between the side frame members.
 18. Thevehicle seat according to claim 17, wherein said elastic meanscomprising two torsion bar springs.
 19. The vehicle seat according toclaim 18, wherein said two torsion bar springs are used in the state ofproducing torque different from each other.
 20. A vehicle seatcomprising: a framework which includes a pair of left and right sideframe members extending in a back-and-forth direction, a front framemember having left and right side plates fixed to front portions of theside frame members, respectively, and a rear frame member having leftand right side plates fixed to rear portions of the side frame members,respectively; a height control mechanism arranged to move the frameworkup and down relative to a vehicle body, said height control mechanismcomprising front and rear arms which connect the framework to thevehicle body, an elongated link which is connected to the rear arm andextends in the back-and-forth direction, and operating means that isconnected to a front end of the elongated link to move the elongatedlink in the back-and-forth direction; said operating means comprising anoutput gear which is rotated by motor power and a link gear which ismeshed with the output gear and is connected to the front end of theelongated link; said height control mechanism further comprising elasticmeans which urges the link gear in a given direction, and said elasticmeans including a laterally extending torsion bar spring which has alength longer than half the distance between the side frame members. 21.The vehicle seat according to claim 20, wherein said elastic meanscomprising two torsion bar springs.
 22. The vehicle seat according toclaim 21, wherein said two torsion bar springs are used in the state ofproducing torque different from each other.